Studies on the lecithin: cholesterol acyltransferase substrate properties of HDL as determined by its subclass distribution analysed by gradient gel electrophoresis

In order to study the impact of high-density lipoproteins (HDL) subclasses on the ability of HDL to act as substrate for lecithin: cholesterol acyltransferase (LCAT), we isolated HDL from nine normolipidemic male subjects. The HDL particle size distribution was analysed by gradient gel electrophoresis and the esterification rate of the isolated homologous HDL was compared with a pool of HDL where all the nine subjects took part. It was found that the strongest determinant for HDL cholesterol esterification rate was the inhibitory action of HDL subclass 2B.     

Many gene and domain families have convergent fates following independent whole-genome duplication events in Arabidopsis, Oryza, Saccharomyces and Tetraodon

Genome duplication is potentially a good source of new genes, but such genes take time to evolve. We have found a group of "duplication-resistant" genes, which have undergone convergent restoration to singleton status following several independent genome duplications. Restoration of duplication-resistant genes to singleton status could be important to long-term survival of a polyploid lineage. Angiosperms show more frequent polyploidization and a higher degree of duplicate gene preservation than other paleopolyploids, making them well-suited to further study of duplication-resistant genes.     

Responses of eight boreal flat bug (Heteroptera: Aradidae) species to clear-cutting and forest fire

Boreal flat bugs include a high proportion of species that are considered negatively affected by forestry. Knowledge on the biology and habitat demands of individual species is generally limited. We examined the influence on flat bugs of stand-age and clear-cutting, comparing five classes of spruce stands. The five classes were: clear-cut, unthinned, and thinned (all three products of current clear-cutting forestry), mature managed and old-growth stands (these two had never been clear-cut). We also compared unburned and recently burned mature pine forest. Fire, but not stand age, had a pronounced effect on species richness and total abundance. Aradus depressus showed a significant association with older forest stands. Aradus betulae occurred only in clear-cuts and burned forest indicating that this species is favored by disturbance in general. Aradus lugubris, Aradus crenaticollis and Aradus brevicollis were found only in the burned forest. Aradus brevicollis has not previously been shown to be associated with fire.     

Type IVB secretion by intracellular pathogens

A growing number of pathogens are being found to possess specialized secretion systems which they use in various ways to subvert host defenses. One class, called type IV, are defined as having homology to the conjugal transfer systems of naturally occurring plasmids. It has been proposed that pathogens with type IV secretion systems have acquired and adapted the conjugal transfer systems of plasmids and now use them to export toxins. Several well-characterized intracellular pathogens, including Legionella pneumophila , Coxiella burnetii , Brucella abortus , and Rickettsia prowazekii , contain type IV systems which are known or suspected to be of critical importance in their ability to cause disease. Specifically, these systems are believed to be the key factors determining intracellular fate, and thus the ability to replicate and cause disease.     

Adaptation to intermittent stress promotes maintenance of beta-cell compensation: comparison with food restriction

Intermittent restraint stress delays hyperglycemia in ZDF rats better than pair feeding. We hypothesized that intermittent stress would preserve beta-cell mass through distinct mechanisms from food restriction. We studied temporal effects of intermittent stress on beta-cell compensation during pre-, early, and late diabetes. Six-week-old obese male ZDF rats were restraint-stressed 1 h/day, 5 days/wk for 0, 3, 6, or 13 wk and compared with age-matched obese ZDF rats that had been food restricted for 13 wk, and 19-wk-old lean ZDF rats. Thirteen weeks of stress and food restriction lowered cumulative food intake 10-15%. Obese islets were fibrotic and disorganized and not improved by stress or food restriction. Obese pancreata had islet hyperplasia and showed evidence of neogenesis, but by 19 wk old beta-cell mass was not increased, and islets had fewer beta-cells that were hypertrophic. Both stress and food restriction partially preserved beta-cell mass at 19 wk old via islet hypertrophy, whereas stress additionally lowered alpha-cell mass. Concomitant with maintenance of insulin responses to glucose, stress delayed the sixfold decline in beta-cell proliferation and reduced beta-cell hypertrophy, translating into 30% more beta-cells per islet after 13 wk. In contrast, food restriction did not improve insulin responses or beta-cell hyperplasia, exacerbated beta-cell hypertrophy, and resulted in fewer beta-cells and greater alpha-cell mass than with stress. Thus, preservation of beta-cell mass with adaptation to intermittent stress is related to beta-cell hyperplasia, maintenance of insulin responses to glucose, and reductions in alpha-cell mass that do not occur with food restriction.     

A major shift in diversification rate helps explain macroevolutionary patterns in primate species diversity

Primates represent one of the most species rich, wide ranging, and ecologically diverse clades of mammals. What major macroevolutionary factors have driven their diversification and contributed to the modern distribution of primate species remains widely debated. We employed phylogenetic comparative methods to examine the role of clade age and evolutionary rate heterogeneity in the modern distribution of species diversity of Primates. Primate diversification has accelerated since its origin, with decreased extinction leading to a shift to even higher evolutionary rates in the most species rich family (Cercopithecidae). Older primate clades tended to be more diverse, however a shift in evolutionary rate was necessary to adequately explain the imbalance in species diversity. Species richness was also poorly explained by geographic distribution, especially once clade age and evolutionary rate shifts were accounted for, and may relate instead to other ecological factors. The global distribution of primate species diversity appears to have been strongly impacted by heterogeneity in evolutionary rates.     

Sustained neurochemical plasticity in central terminals of mouse DRG neurons following colitis

Sensitization of dorsal root ganglia (DRG) neurons is an important mechanism underlying the expression of chronic abdominal pain caused by intestinal inflammation. Most studies have focused on changes in the peripheral terminals of DRG neurons in the inflamed intestine but recent evidence suggests that the sprouting of central nerve terminals in the dorsal horn is also important. Therefore, we examine the time course and reversibility of changes in the distribution of immunoreactivity for substance P (SP), a marker of the central terminals of DRG neurons, in the spinal cord during and following dextran sulphate sodium (DSS)-induced colitis in mice. Acute and chronic treatment with DSS significantly increased SP immunoreactivity in thoracic and lumbosacral spinal cord segments. This increase developed over several weeks and was evident in both the superficial laminae of the dorsal horn and in lamina X. These increases persisted for 5 weeks following cessation of both the acute and chronic models. The increase in SP immunoreactivity was not observed in segments of the cervical spinal cord, which were not innervated by the axons of colonic afferent neurons. DRG neurons dissociated following acute DSS-colitis exhibited increased neurite sprouting compared with neurons dissociated from control mice. These data suggest significant colitis-induced enhancements in neuropeptide expression in DRG neuron central terminals. Such neurotransmitter plasticity persists beyond the period of active inflammation and might contribute to a sustained increase in nociceptive signaling following the resolution of inflammation.     

Effect of Eyestalk-Ablation on Circulating Ecdysteroids in Hemolymph of Snow Crabs, Chionoecetes opilio: Physiological Evidence for a Terminal Molt

Bering Sea snow crabs (Chionoecetes opilio) are a commerciallyimportant crab harvested in the Bering Sea. Optimal managementof this species requires an understanding of the biology ofthis crab that is currently incomplete. Fisheries managers applya continuous growth model in their management of snow crab,which assumes that male crabs increase in size throughout theirlifespan. Male snow crabs undergo a morphometric molt that leadsto a disproportionate increase in chelae size and it is stilldebated whether this molt is associated with a terminal molt.This study was conducted to determine whether adult male C.opilio are anecdysic. Using current knowledge of the hormonalregulation of crustacean growth, snow crab physiology was manipulatedto induce an increase in molting hormones (ecdysteroids). Sincefemale snow crabs are known to undergo a terminal molt afterattaining reproductive maturity, we compared ecdysteroid levelsin eyestalk-ablated terminally molted females, small-clawedmales and large-clawed males. Snow crabs were collected fromthe Bering Sea and maintained in circulating seawater at approximately6°C. Animals were either eyestalk-ablated or left intact.Ecdysteroid levels in hemolymph were quantified using an enzyme-linkedimmunosorbant assay (ELISA). Circulating ecdysteroids were significantlyhigher in small-clawed male crabs when compared to large-clawedmales or terminally molted females. Eyestalk-ablation increasedcirculating ecdysteroids in small-clawed males, but had no significanteffect on circulating ecdysteroids in large-clawed males orin terminally molted females.